...really?

I suppose that every game besides 4U is a spinoff then, because MH games actually having a plot is VERY much the exception rather than the rule.

MH/MHF: you are the new hunter, go hunt monsters

MHDos/MHF2/MHFU: Pokke village has a tiggy problem, go fix it.

MHTri/MH3U: Moga village has an earthquake problem, kill lagiacrus. PSYCHE it was cedaeus, go kill it now

MHP3rd: Yukumo has a jinouga problem, go kill it. PSYCHE it was amatsumagasutchi, go kill it now

MH4/MH4U: you are a hunter travelling the world with a caravan, solving problems for various villages, you are part of a vague prophecy involving the return of shagaru magala and must investigate the appearence of unusual monsters that are more aggressive and do not die. after you are sent to figure out why seregios are acting strangely, only to find that they are being driven from their homes by the biggest, baddest seregios around, infected by the same disease that shagaru carried

MHGen: four villages have monster problems ruining their tourism industries. go kill the monsters.